Method of manufacturing wire staples



Oct. 28 1958 s. .1. MASHL METHOD OF MANUFACTURING WIRE STAPLES FiledSept. 8, 195::

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United States Patent METHOD MANUFACTURING WIRE STAPLES Stephen J. Mash],Bradford, Westerly, R. L, assignor to Bostitch, Inc., Stonington, Conn.,a corporation of Rhode Island Application September 8, 1953, Serial No.378,747

1 Claim. (Cl. 59-77) This invention relates to the manufacture of Wirestaples and similar fasteners and more particularly to a method offorming U-shaped staples to increase their strength and resistance todistortion or becoming malformed as they are driven into the work.

One object of the invention is to so form the staples at the points ofjoinder of their legs with the ends of the head or crossbar as to avoidweakening the wire or other strip-material at the bent portions therein.

Another object is to form the staples by bending the wire or otherstrip-material in such manner that the material is not unduly stretchedor elongated to reduce its thickness or diameter along the shoulders atthe angular bends therein.

Another object is to provide an improved form of staple possessingconsiderably greater strength and rigidity than conventional staples atthe points of joinder of the legs with the head or crossbar.

Another object is to provide an improved staple less liable to becomemalformed or misshaped in the operation of driving it into the work.

Another object is to provide an improved staple or fastener capable ofsuccessful penetration into relatively hard and unyielding materialswithout buckling at its head or becoming distorted in shape.

Another object is to provide a novel and improved method of formingstaples to secure increased strength and stiffness or rigidity thereinand ensure their easier penetration into hard materials offeringconsiderable resistance to driving.

Another object is to provide an improved staple that is stronger andmore rigid when constructed from wire of smaller gauge than previouslyused for staples of conventional type while still possessing thenecessary qualifications for driving into thick, hard materials withoutcausing the wire to bend or buckle at the points of joinder between thelegs and the head.

Staples and similar fasteners of inverted U-shape are commonlymanufactured, or formed in stitching machines, from continuous lengthsof wire and relatively thin metal strip-material by cutting it intoshort lengths and bending the legs at substantially right-angles to thecentral crossbar or head. During the forming or bending of the staplelegs the wire or other strip-material must be stretched or extendedaround the outer periphery of the shoulders in the relatively sharpbends between each end of the crossbar and the right-angularleg-portions. Such stretching of the metal along one side of the arcweakens the material by reducing its crosssectional area, as can beobserved by examining an ordinary staple under a magnifying glass. Thisthinning of the wire or strip at the bend can also be shown bycomparative tests with a micrometer caliper of proper type. Moreover,this stretching of the wire may very well disturb or disrupt themolecular cohesion in the grain of the metal.

The reduction in thickness of the wire or other strip Patented Oct. 28,1958 and its consequent weakening in the shoulders at the top of thestaple legs frequently causes buckling of the wire at these points,especially when attempt is made to drive the staple into relatively hardmaterial or through work of extreme thickness. In some cases, during thedriving of the staple the wire will be doubled on itself or bent aroundin a hairpin loop adjacent the shoulders at the end of the head, therebyrendering the staple malformed and unfit for use. Furthermore, eventhough the staple may be applied to the work properly, should it becomenecessary or desirable to extract or withdraw it, the insertion of aninstrument under its head to pry it out usually results in fracturingone of its shoulders, a common experience.

To overcome these present defects or deficiencies in common types ofU-shaped fasteners or wire staples I have devised a method of formingstaples without materially weakening the wireor other trip-material atthe bends which connect the legs with the ends of the head or crossbar.

The present novel method for forming staples and the improved stapleproduced thereby are described in the following specificationillustrated by the accompanying drawing, in which:

Fig. 1 is a side view of a staple of conventional type showing myimprovement applied thereto;

Fig. 2 is a view of the wire blank from which the staple may be formed,indicating in dotted lines the first step in the present improved methodfor bending the wire to form the legs at the ends of the head orcrossbar;

Fig. 3 is a view showing in full lines the first step in the improvedmethod for bending the wire and indicating in dotted lines the second orfinal step for bending the wire to form a U-shaped staple of maximumstrength and rigidity;

Fig. 4 is a greatly enlarged fragmentary view of the bent portion orshoulder at the top of one leg of the improved staple;

Fig. 5 is a view similar to Fig. 1 showing the present improved stapleas having a somewhat different shape in its crossbar or head assometimes used in the art; and

Fig. 6 is a side view ofthe present improved staple showing stillanother variation in the shape of its erossbar or crown.

As has been stated, U-shaped staples are manufactured by cuttingcontinuous lengths of wire or other metal strips into relatively shortlengths or blanks, in accordance with the size of staple to be produced,and bending the ends of the blank at substantially right-angles to itsmain portion to form the opposite legs.

The staple-forming operations may be performed in a drop-press or othertool by the use of suitable dies; while in other instances the wire maybe cut into short lengths and bent to form the staples in awire-stitching machine immediately prior to driving the staples into thework. Any suitable means may be employed for continuously producingstaples by the present improved method of forming the wire to embody theadvantages of the present invention and secure a stronger and more rigidstructure in the staple itself.

As shown in Fig. 2, a length of wire or other stripmaterial may form theblank 2 from which the improved staple is to be formed by the presentmethod as next explained. As a first step for forming the legs of thestaple the strip or blank 2 is bent at two points spaced inwardly fromits ends, and indicated at aa in Fig. 2, to incline the end-portion 3, 3of the wire downwardly at an angle of substantially forty-five degrees,represented by dotted lines in Fig. 2 and full lines in Fig. 3. At thenext step the end-portions 3, 3 of the blank 2 are bent at points b-b,located slightly outwardly beyond the first bends at 3. a-a,, to force.the end portionsof the wire downwardly another forty-five degrees so.they will stand at ninety degrees to the crossbar or head 4 of thestaple to form the oppositeparallel legs 5, 5 of the staple asdelineated in Fig. 1. These. bending operations may beperformed by a:substantially continuousstroke of the plunger in a die or other toolhaving an anvil of proper dimensions constructed from. a hardened steelblock with its edges at the sides beveled or chamfered to preserve shortstraight lengths 6, 6 of'the wire on theinner sides of the bends orshoulders 7, 7 as shown most clearly in the enlarged view, Fig. 4. By.this method of forming the blank the diameter of. the wire orstrip-material is not reducedito any appreciable'extent by stretchingthe material alongthe outer curved. length 011 the bend or shoulder 7.

With this improved method of forming the staples the bends at the endsof the head or crossbar are not weakened. because the. cross-sectionalarea is maintained substantially uniform with that of remaining portionsof the material in the head and legs of the staple. This fact has beendemonstrated by technical analyses and proven by tests in actualpractice. Staples producedby the present improved method or process offorming them from wire or like strip-material can be driven intoextremely hard substances, for example steel, and through work ofconsiderable thickness without danger of buckling the wire at theshoulders or otherwise distorting the. original shape of the staple. Ithas also been found that when it is necessary to extract or withdraw aclinched staple of the present improved type by prying it out of thework with a tool inserted under its head, the strain on the wire issuccessfully resisted'withoutchance of fracture at the shoulders orbends in the wire as is often the case with conventional types ofstaples at present in use.

While the present improvement is hereinillustrated and describedasapplied to a conventional type of. staple such as illustrated in Fig.1, and two modified forms having differently shaped heads, see Fig. 5where the head is shown as bowed downwardly, and Fig. 6 where the headis illustrated as arched upwardly in a central crown,.it is further tobe understood that fasteners of still othertypes are adaptable for theapplication of the present improvement thereto within the purview andscope of the invention. For example, the present improved staples. mayhave their legs curved or bent according to various configurations.Moreover, the present invention may be applied tothe manufacture offasteners having a head with only a single leg at one end. It is alsoconceivable that the present improved staple may have its legs formed bybending the end portions of the wire blank in three or more distinctsteps or stages; that is, initially at an angle of less than forty-fivedegrees and subsequently at two additional points along the wire inequal angles thereby resulting in three substantially straight shortlengths in the wire on the inside of each shoulder.

Therefore, without limiting myself to the exact steps of the method offorming staples as set forth above or to the exact shape of the stapleas herein described, I claim:

An improved method of manufacturing staples and fasteners of similarshapeconsisting in providing a length of bendable wire or likestrip-material, bending the wire through a first angle of substantially45 degrees at a point inwardly from the end of said length to form a legportion while confining the wire on the inside of the bend, continuingthe confinement of the material and bending it through a second angle ofsubstantially 45 degrees at a point slightly beyond the point of thefirst bend to cause the leg to extend substantially perpendicular to thehead of the staple, the distance between said bends being not materiallygreater than the thickness of the wire with the inner side of'the bentlength straight and the outer perimeter of said length of circularconfiguration, said inner straight side forming substantially a chord ofthe arc of the circular outer perimeter, said bending operationsbeing-so performed as to minimally diminish the cross-sectional area ofthe Wire at the points of bending.

References Cited in the file of this patent UNITED STATES PATENTS257,565 Dunn May. 9, 1882 1,001,529 Jonah Aug. 22, 1911 1,443,828 BaileyJan. 30, 1923 1,792,235 Maynard Feb. 10, 1931 2,052,553 Cavanagh Sept.1, 1936 2,067,359 Tumminello Jan. 12, 1937 2,343,933 Saul Mar. 14, 19442,380,786 Percoco July 31, 1945 2,521,019 Percoco Sept. 5, 19502,528,685 Brown Nov. 7, 1950 2,632,356 Thiel Mar. 23, 1953

